Engine start simulation



Dec. 12, 1961 R. A. ATcHIsoN ETAL 3,012,338

ENGINE START SIMULATION Filed April 29, 1958 2 Sheets-Sheet 1 ATT ORNE y Dec. 12, 1961 R. A. A'rcHlsoN ETAL 3,012,338

ENGINE START SIMULATION 2 Sheets-Sheet 2 Filed April 29. 1958 NWI Oll'll om mm1 IIIIIIIILIlI-IIIIIIII QORO INVENTORS. GEORGE R. SOM/TER ROBERT A. ATCH/SON ATTORNEY United States Patent Office 3,012,338 Patented Dec. 12, 1961 3,012,338 ENGINE START SMULATION Robert A. Atchison, Titusville, Fla., and George R.

Sowter, Silver Spring, Md., assiguors to ACF Industries,

Incorporated, New York, N.Y., a corporation of New Jersey Filed Apr. 29, 1958, Ser. No. 731,747 4 Claims. (Cl. 35-12) This invention relates to a system for simulating aircraft operation, and more particularly to a circuit for simulating the starting procedure for an aircraft having a plurality of jet engines.

in an actual jet powered aircraft, the pilothas comparatively few controls since most of the starting sequencing is accomplished automatically. However, the pilot usually has engine starting switches, one for each engine, and an engine lire switch for each engine. The start switches usually have a plurality of positions for selection, one for ight start, one for ground start and a center OE position. The first switches are normally placed in the Ott position during flight but Vwhen the pilot receives an indication of iire he actuates the respective switch which acts to cut voff fuel, ignition, and hydraulic connections to that engine and the engine stops. The throttle must be placed in a predetermined start position to insure fuel supply for engine starting.

A primary object of the invention, therefore, is to provide in -a grounded iiight simulator a system for realistically simulating the starting procedure of a multijetengine aircraft.

A more speciiic object of the invention is to provide an engine starting simulating circuit consisting of an inter-related network of relays, switches and a servomechanism which permits simulated engine starting only when proper conditions are met.

The invention embodies other novel features, details of construction and arrangement of parts which are hereinafter set forth in the specification and claims and illustrated in the accompanying drawings which are hereby made a part of the specification, wherein:

FIG. 1 is a block diagram of a system embodying the engine starting circuit.

FIG. 2 is a schematic diagramV of a portion of the circuit of FIG. 1 showing the details of the simulated air-cranking system.

In general, three types of engine starts in an actual aircraft are possible air start; ground start from high pressure air container; and ground start from air bled from another engine. Usually for ground starting, one engine is arranged to be started from a high pressure air accumulator and the other engines are started with air bled from that engine once it is operating.

This invention finds its preferred setting in Ia grounded aircraft trainer of the type having computers to derive voltages proportional to functions of altitude, Mach number, fuel iiow, and engine r.p.m., all of which are known in the simulator art. It will also be understood that the student pilot has available for his manipulation, a series of simulated controls; `for example, a throttle which is positionable for a starting and running cycle. An engine noise simulator is usually provided.

Referring now to the drawings wherein mechanical connections are shown in broken lines and electrical connections are shown in solid lines, starting at the righthand side of FIG. l, reference character 10 designates a relay representing engine starting, and connectable through a plurality of individual contacts to the fuel ow computer, the sound simulator, the engine rpm. computer so that upon closing of the relay, the trainee sees instruments which reveal the dynamic engine characteristics and hears the usual jet engine noises.

The actual engine is responsive to a plurality of Vprerequisite starting conditions, all of which must be satisfied before engine combustion is obtained. Referring to the left-hand side of the drawing, -a source of energy at terminal 12, is impressed upon the operating coil of the engine start relay 1t) only after iive series connected circuit interrupters have closed. Referring to the interrupters yfrom left to right, reference character 13 designat-es a failure switch available to the instructor at his position in the trainer land manually operated to simulate the condition of engine failure during iiight or to prevent start to determine the reaction of the trainee. Reference character 14 designates a fuel flow relay responsive to operation of a prior art fuel ow computer 15 which may comprise a position servomechanism to close and thereby complete the circuit to an r.p.m. switch 16 which is responsive to the operation of a prior art rpm. computer 17. Switch 16 is mechanically coupled to computer 17 and will open when the engine r.p.m. is zero.

A relay representing engine blow-out 18 is connected to the rpm. switch as there shownand is responsive to predetermined conditions of simulated iiight altitude and Mach to open and thereby simulate blow-out of the engine.

A well known characteristic of jet engines is that at certain combinations of altitude and speed they will fail because the oxygen supply is insuii'icient to support combustion. Here, an altitude computer 51 and a Mach number computer 50 derive voltages proportional to simulated ihght conditions, and a selector circuit 55 compares input voltages and amplies the resultant to control an output tube which, in turn, controls a relay. This relay causes the blow-out relay 18 to open when the iiight is in simulated blow-out condition. A conductor 53 applies the output from selector 55 to the blow-out relays of the remaining engines.

A relay representing engine ignition 19, connects the blow-out relay 1S and the engine start relay 1t) and will close only when voltage is impressed upon its operating coil. The path of energy for this coil is from switches 47 and 22, throttle 21, through the operating coil to land-air relay 2t) where a ground connection is made when the simulated aircraft is on the ground; or if in iiight, a ground connection is made if the altitude and Mach number computers are deriving voltages of such magnitude as to permit a flight start.

The engine start relayy 1i) is connected to the ignition rela* but in order to maintain the engine in a simulated operating condition after the ignition has turned oi, a self maintaining contact 23 transmits voltage from the input side of relay 19 to hold relay 10 energized once the Yignition cycle has taken place and simulated enginev is started.

A relay 41 representing the engine cranking, has contacts leading to the sound simulator to realistically reproduce to the trainee the noises made by an engine during cranking and has contacts to energize the engine r.p.m. computer 17 which closes switch 16 when the computer simulates engine turning.

As in the actual aircraft, it is possible to select between a number of ways of starting the engine when the craft is on the ground. There is a high pressure air accumulator which is here simulated as circuit 42 and will be explained in detail in connection with FIG. 2, and there is an air-bleed relay 43 usable to start an engine if another engine is running and high pressure air is available. If the pilot moves selector switch 22 to the ground start position and selector switch 44 to the air-bleed relay position, then relay 43 will close relay 41 with the resultant engine cranking cycle. only if switches 44 and 45 which pressure decreasing direction. .and 49 are so chosen that the motor runs more rapidly in therpressure decreasing direction than in the pressure increasing direction to simulate the elect of a large drain aoiasaa respectively represent the open condition of bleed valve and bleed air available are closed.

A fire switch 47 is provided in the trainees station, one for each engine, endif the indications of lire condition appear on his instrument panel, his expected response is to open the switch 47 which interrupts simulated fuel Jlow which opens the fuel llow relay and opens start relay it?. If during simulated night, the pilot has a condition Vof engine failure and wishes to start the engine, he will first insure that tire switch 4'7 is in the normal position and will then move switch 22 to the flight start position. lThis will automatically open-circuit all connections tothe engine cranking relay 4l, and apply energy through the throttle contact 21 to one side of the operating coil of ignition relay 19. The throttle contact 21 will actuate the Vfuel ow computer which will close the fuel rlow relay 14. if the engine is windmilling, the rpm. cornputer will keep switch lo closed and if the altitude and Mach number of simulated flight are such that the respective selectors 26 and 55 close their circuits, then the blow-out relay i8 is in closed position and the ignition f relay operating coil circuit is completed through the landair relay 20 through selector 26 to ground. The ignition l relay will now close and energize the operating coil of connected to the moving element of pressure indicator 3i, is'provided to give Van indication of the pressure of the air available for starting and to realistically reduce the indicated pressure during starting cycles and thereafter turn o the engine cranking relay to prohibit further Astarts until the air supply is again charged. An instructors switch 32` has a charge and discharge position and Va pair of relays 33 and 34 and arranged to respectively operate motor '29 in either direction. A limit switch 36 is mechanically connected to shaft 30 to terminate motor operation in the high pressure position and klimit switch 3-7 is mechanically connected to shaft Bilto terminate motor operation in the low pressure position. Limit switch 3S is provided to open the circuit to the engine cranking relay when pressure is too low for cranking.

If the pressure gauge 31 indicates low pressure, the instructor will move selector switch 32 to the charge position which energizes the operating coil of relay 33 thereby moving the double contacts down and opening the circuit to the starting switch and connecting from a source of energy through a resistor 4i), todetermine the rate of rotation of the motor in pressure increasing direction, through closed limit switch 36, through upper con- .tact of relay 33, and motor 29 to ground. This causes motor 29 to run in a simulated pressure increasing direction and moves the element of gauge 31 toward the high pressure position. The motor will run until limit switch 36 opens thereby removing energy from motor 29. If

. now the student attempts to start the engine, the starting relay cannot close unless the instructor has moved selector switch 32 to the Ol position thereby deenergizing 34. The contact of relay 34 moves to its lower position applying energy from a source of voltage through motor running rate resistor 9 to motor 29 which runs and causes the movable element of gauge 31 to move to a simulated The values of resistors V9 (position, the engine will fail to start and the trainee may continue to attempt-to start the engine, the cranking continuing to move the gauge in a pressure decreasing direction until limit switch 38 opens its circuit and cuts oi energy to the engine cranking relay. No further engine starts are possible in this condition. If the trainee persists in attempting to start 'the engine, the down limit switch 37 will open the circuit and motor 29 will stop.

The instructor may, at his election, Vdischarge the air supply by moving his selector switch to the discharge position to simulate leakage of the accumulator. This operationapplies a voltage to the operating coil of relay 34 and applies a voltage through the relay contact to operate motor Z9v in the simulated pressure decreasing direction. v

Having described a preferred embodiment of the present invention, it is to be understood that although specic terms and examples areA employed, they are used in a generic and descriptive sense and not for purposes of limitation; the scope of the invention being set forth in the following claims:

What is claimed is:

l. ln a grounded aircraft trainer of the type having means to lsimulate the functioning of an array of jet engines each responsive to a plurality of prerequisite starting conditions, a rst circuit for simulating the starting of an engine comprising in combination means operable by a trainee for position selection according to simulated night ,or ground condition, and a second circuit to actuate the engine functioning means after a predetermined operational sequence, said second circuit comprising a relay to represent engine cranking, a third circuit representing a source of starting air connected between the position selection means and the cranking relay, arelay representing engine ignition, a simulated throttle control means for closing said ignition relay, a relay representing engine starting having a coil connected to the ignition relay and contacts connected to the engine `functioning means and closeable in responseV to operation of the said ignition relay, said third circuit comprising a servo having a shaft movable to a position representing starting Vair supply, and an interrupter electrically connected to said engine cranking relay and mechanically connected simulated air exhausted condition to thereby disable the cranking relay and terminate further attempted engine .starting cycles.

'2. A grounded aircraft trainer comprising a simulated throttle control, computers to derive voltages proportional to functions of altitude and Mach number, means to simulate the operation of a series of jet engines each responsive to a plurality of prerequisite starting conditions, a circuit for simulating the starting of an engine comprising in combination a switch operable by a trainee for position selection according to simulated night or ground condition, and a circuit'to actuate the engine operating means after a predetermined operational sequence, lSaid circuit comprising a relay representing engine crankling connected to said switch, a pair of circuit interrupters representing fuel now and engine rpm. connected in series relationship to a source of electrical energy, means for closing said interrupters in response to operation of the engine cranking relay, a normally closed relay representing nightY blow-out having contacts V'connected in Vseries with the said pair of circuit interrupters and means responsive vto the altitude and Mach number computers for opening theblow-out relay only under predetermined simulated flightV conditions, Va relay representing engine ignition having contacts connectedin series with the contacts of the said blow-out relay and means for closing the ignition relay Vin response to the altitude and Mach cornputers and manipulation of the simulated throttle control under predetermined flight conditions, and a relay representing engine starting having a winding connected tothe said ignitionrrelay and having contacts connected to the engine operation means and closeable in response to actuation of the said ignition relay.v

3. In a grounded aircraft trainer of the type having computers to derive voltages proportional to functions of Y,altitude and Mach number and having aural and visual to the shaft to be opened when the shaft moves to a Y ing relay and means to simulate to a student the operation of a group of jet engines each responsive to a plurality of prerequisite starting conditions, a circuit for simulating the starting of a jet engine comprising in combination a switch operable by a trainee tor position selection according to sirnuiated iiight or ground condition, and a circuit to actuate the engine operating means after a predeterrnined operational sequence, said circuit comprising a simulated throttle control, a relay representing engine cranking, electrical rneans representing at least one source of cranking energy connected eti/veen the engine crankthc said switch to close the said engine cranking relay, a pair of circuit interrupters representing fuel ow and engine rpm. and means for closing the interrupters in response to operation of the engine cranking relay, a normally `closed relay representing flight blow-out having contacts connected to the said pair of interrupters and a Winding connected to the altitude and M ch number computers and arranged to open only under predetermined simulated flight conditions, a relay representing engine ignition having contacts connected to the contacts of said last recited relay and a Winding connected to the altitude and Mach number computers and means for closing said ignition relay in response to manipulation of the simulated throttle 4control under predetermined ight conditions, and a relay representing engine starting having actuating means connected to the said ignition relay and contacts connected to the engine operation means and closeable in response to actuation of the said ignition relay.

4. A grounded aircraft trainer comprising means to simulate the functioning of a plurality of jet engines each responsive to a series of prerequisite starting conditions, a circuit for simulating the starting of each respective engine comprising in combination a switc'n operable by a trainee for position selection according to simulated iiight condition, and a circuit to actuate the engine functioning means after a predetermined operational sequence, said circuit comprising a relay to represent 'engine cranking, a circuit representing a source of available bleed air connected to the position selection switch, the engine cranking relay and to a second respective engine simulating circuit, a relay representing engine rpm. connected to the engine cranking relay for closure in response to operation of said engine cranking relay, a relay representing engine ignition, simulated throttle controi means connected to lthe ignition relay for closing it in response to motion to a predetermined position of the simulated throttle control means, and a relay representing engine starting connected to the ignition relay and to the engine functioning means and closable in response to operation of said ignition relay, the said circuit representing a source of available lbleed air including a switch representing the position of a bleed valve and closable by a trainee.

References Cited in the tile of this patent UNITED STATES PATENTS 2,608,005 Kennedy Aug. 26, i952 2,798,38 Stern et al. July 9, 1957 2,882,615 Dawson Apr. 2l, 1959 

